Advantages of Fourier Transform

From Table 2 it is observed that the dispersive NIR ensembles (NIR and NIR R) result in the best cross validated models. The potential advantages of Fourier transform spectroscopy [5] are in practice outnumbered by a more reproducible setup and saimpling procedures. 

Advantages of Fourier transform infrared spectrometers are so great that it is nearly impossible to purchase a dispersive infrared spectrometer. Fourier transform visible and ultraviolet spectrometers are not commercially available, because of the requirement to sample the interferometer at intervals of S = l/(2Av). For visible spectroscopy, Av could be 25 000 cm 1 (corresponding to 400 nm), giving S = 0.2 im and a mirror movement of 0.1 xm between data points. Such fine control over significant ranges of mirror motion is not feasible. 

An advantage of Fourier transform spectroscopy is that the entire interferogram is recorded in a few seconds and stored in a computer. The signal-to-noise ratio can be improved by collecting tens or hundreds of interferograms and averaging them. 

The classical approach to the analysis of mixtures by use of infrared spectroscopy consists in identifying specific, strong bands that belong to a suspected component, obtain a pure spectrum of the suspected component, and then remove those in the spectrum of the mixture that are due to the identified compound. The process is repeated for the remaining bands in the mixture spectra. Once the component spectra are known for a mixture, a series of calibration curves is produced. These curves relate concentration to absorbance, using Beer s law. The concentration of the components of the mixture are then obtained by interpolation. The advantage of Fourier-transform, infrared spectroscopy is that components of a mixture may be... 

The second advantage of Fourier transform instruments is the so-called multiplex advantage. This is related to the fact that in a Fourier transform spectrometer, in con-... 

What are the major advantages of Fourier transform IR instruments over dispersive IR instruments ... 

Many of the advantages of Fourier transform infrared (FT-IR) over dispersive infrared also apply to FT-Raman over conventional Raman, for example signal averaging and spectral subtractions, together with all frequencies are measured simultaneously and hence there is increased speed of analysis. 

One advantage of Fourier transform NMR becomes immediately obvious. Consider an analogy Suppose there were a... 

In recent years, new schemes have been introduced in Raman studies, taking advantage of Fourier transform spectrometers and of lasers. For instance CARS techniques can now achieve nominal resolutions of 0.003 to 0.005 cm" with accuracies of 0.001 cm" or better. Unfortunately, these experiments are still limited to a small number of skilled laboratories. Nevertheless, joint works using both IR and Raman data are found now, Raman being especially usefnl for infrared inactive bands. 

The advantages of Fourier transform near-infrared Raman spectroscopy are ... 

A second advantage of Fourier transform instruments is their extremely high resolving power and wavelength reproducibility that make possible the analysis of complex spectra in which the sheer number of lines and spectral overlap make the determination of individual spectral features difficult. Figure 7-40. which is papt of an emission spectrum for a steel, illustrates this advantage. The spectrum, which extends from only 299.85 to 300.75 nm, contains thirteen well-separated lines of three elements. The wavelength resolution (AA/A) for the closest pair of lines is about 6 ppm. 

The advantages of Fourier transform spectrometry over the use of a scanning monochromator (often referred to as dispersive spectrometry) is fully valid only when the detector noise is independent of the power of the radiation incident on the detector. When the detector is photon shot-noise limited [as it generally is for a photomultiplier tube (PMT), and often is for other sensitive detectors used in the near-infrared, visible, and ultraviolet spectral regions], the noise level is proportional to the square root of the incident power. For a boxcar spectrum, this means that shot noise is proportional to the square root of the number of resolution elements in the spectrum, This disadvantage therefore precisely offsets Fellgett s advantage when continuous broadband sources are employed. It should also be... 

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